Molecular Soil Biology 2024, Vol.15, No.4, 183-192 http://bioscipublisher.com/index.php/msb 188 of soil enzymes varied with Bt crop types and growth periods, with the strongest effects observed under Bt cotton (Li et al., 2019). Additionally, a review of global resistance monitoring data for Bt crops revealed that practical resistance has been documented in some pest populations across seven countries, affecting various Bt toxins (Tabashnik et al., 2023). These regional differences underscore the need for localized studies to understand the specific environmental impacts of Bt crops in different contexts. Figure 2 Long-term effects of Bt-transgenic rice on bacterial communities in different plant niches: a three-year study (Adapted from Wu et al., 2021) 8 Regulatory and Environmental Considerations 8.1 Current regulatory guidelines on Bt use and microbial safety Current regulatory guidelines for the use of Bacillus thuringiensis (Bt) and its associated products, such as Bt transgenic crops and Bt biopesticides, emphasize the need for comprehensive biosafety evaluations before their approval for field tests and commercial production. These evaluations are crucial due to the potential ecological risks posed by Bt proteins, which are considered environmentally exogenous substances with insecticidal toxicity. Regulatory frameworks typically require detailed assessments of the adsorption, retention, and degradation behaviors of Bt proteins in soils, as well as their impacts on soil physical and chemical properties and microbial diversity (Li et al., 2022). Additionally, the guidelines mandate the monitoring of non-target organisms, including soil microorganisms, to ensure that Bt applications do not adversely affect soil biodiversity and ecosystem services (Castaldini et al., 2055; Kostov et al., 2014). 8.2 Environmental monitoring practices for Bt toxin residues Environmental monitoring practices for Bt toxin residues involve systematic field and laboratory studies to track the persistence and effects of Bt proteins in soil environments. These practices include the use of various analytical techniques to measure Bt protein concentrations in soil and assess their impact on soil microbial communities. For instance, studies have employed ribosomal DNA-fingerprinting methods and real-time PCR to monitor changes in soil bacterial, fungal, and archaeal diversities and community structures over time (Zhaolei et
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